Millions of cassava farmers in eastern and central Africa are in
distress from viral cassava diseases that are sweeping across the region
and ravaging their crops. But their counterparts on the popular tourist
island of Zanzibar are undergoing a quiet revolution using new
disease-resistant and high-yielding varieties that were introduced three
years ago.

Farmer
Ramadhani Abdala Ame, one of the pilot farmers in Kianga village with
his improved cassava variety that he has uprooted for home use. (Photo
credit: Catherine Njuguna)

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The four varieties, Kizimbani, Mahonda, Kama, and Machui, have given
cassava a new lease on life after the crop was devastated by the two
main diseases afflicting the region: brown streak disease and mosaic
disease. The diseases, which are spread by white flies, cost Africa's
cassava sector more than US$1 billion in damages every year. Small-scale
farmers among the poorest in the region bear most of the economic
effects.

Cassava mosaic disease first appeared in Uganda in the mid-1980s and
spread rapidly in cassava-growing areas of eastern and central Africa
through the sharing of infected planting materials and via the white fly
vector. Following the development and deployment of resistant and
tolerant varieties and widespread awareness-raising on ways to curb the
mosaic's spread, scientists, governments, non-governmental
organizations, and farmers were able to bring the disease nearly under
control. Then the cassava brown streak struck. This disease had been
around for much longer but was confined to the coastal low-altitude
areas of Eastern Africa and around Lake Malawi. From 2004, it started
spreading rapidly to mid-altitude areas that were recovering from the
mosaic, sending scientists back to the drawing board.

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Haji Saleh, the head of Zanzibar's roots and tuber program under the
Ministry of Agriculture, Livestock and Environment, says the first
survey of cassava brown streak on the island was conducted in 1994 and
indicated that 20 percent of the crop had disease symptoms. In a
follow-up survey in 2002, the disease was found everywhere. "All the
local varieties grown by the farmers were susceptible. The farmer and
authorities were crying out for help," Saleh said.

A field
of recently planted cassava cuttings that are starting to sprout leaves.
(Photo credit: Catherine Njuguna)

Heeding the call for help, Zanzibar crop scientists in collaboration
with the International Institute of Tropical Agriculture (IITA) started a
breeding program to develop cassava varieties that were resistant to
the two diseases. Their efforts paid off, and after only four years,
four new varieties were released in 2007.

"You have to understand, cassava is a very important staple in
Zanzibar, where it comes in second after rice," Saleh said. "However, it
is first in terms of acreage and production with over 90 percent of
farmers growing the crop. It is our food security crop as it grows in
most of the agro-ecological zones including in the dry parts of the
island where other crops do not perform well. So when the diseases hit,
they were very devastating to the island's food security. We had to act
fast."

The research team then started a rapid multiplication program,
working with the farmers to spread the improved varieties on the island
and beyond. "We selected pilot farmers in each district to help with the
multiplication," Saleh said. "We trained them on how to grow cassava to
get good yields and maintain soil fertility, and on business skills, as
they were to sell the planting material as a business."

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One farmer, 59-year-old Ramadhani Abdala Ame of Kianga village a
father of 10 participated in the on-farm trials using the improved
varieties. During the trials, the farmers helped the researchers select
not only the best performing varieties, but also those that met farmer
preferences and requirements for various uses of the crops. Ramadhani
said he had given up on cassava, which was suffering from "kensa ya
mhogo," or "cancer of the cassava." Infected by the brown streak
disease, the crop develops a dry rot in its roots the most
economically important part of the plant which makes it useless for
consumption.

"The cassava looked good in the field, but when you harvested, the
roots were rotten and useless, with all your labor and efforts going
down the drain," Ramadhani said. He explained that he was given 40
cuttings of the four new varieties to test on his farm. "At that time,
they did not have names, only numbers. I was amazed at their
performance: the tubers were huge, and had no disease. I selected the
two I liked best that were later renamed Kizimbani and Machui."

Ramadhani said the sale of cassava roots and planting materials has
made a big difference in his life. He has bought two cows to add to his
stock, constructed a cowshed, and is now building a better brick and
iron-sheet house for his family.

Another pilot farmer, Suleiman John Ndebe of Machui village, had also
given up on cassava after 10 years of bad harvests due to the "cancer"
and other pests and diseases such as mealy bug and cassava green mite.
But the varieties given to him at Kizimbazi research station for testing
excited him and motivated him to resume growing the crop. It's a
decision he says he has not regretted.

Danielle Nierenberg, an expert on livestock and sustainability, currently serves as Project Director of Nourishing the Planet for the Worldwatch Institute, a Washington, DC-based environmental think tank. Her knowledge of factory farming and its (more...)